Printed-circuit substrate and its connecting method

ABSTRACT

A printed-circuit substrate is provided with: a film-shaped support base having an electrical insulating property and elasticity, which includes a resin mold section for supporting an IC; a plurality of foil-shaped electrodes which are connected to the IC and supported by the support base in such a manner as to extend toward the periphery of the support base; and an exposed portion which is provided by removing the support base in the direction orthogonal to the foil-shaped electrodes over an entire area of the support base between the IC chip and the periphery thereof so as to expose one portion of each foil-shaped electrode. In the case of connecting the foil-shaped electrodes to electrodes of a printed-circuit substrate by means of soldering, the tips of the foil-shaped electrodes are soldered to the respective electrodes by applying heat and pressure to a part of the support base located on the tip-side of the exposed portions of the foil-shaped electrodes. This arrangement makes it possible to improve the pliability of the exposed portion; therefore, even if the support base is miniaturized to have a thin width by shortening the exposed portion, the reliability of the connecting structure is improved between the tips of the foil-shaped electrodes and the electrodes.

FIELD OF THE INVENTION

The present invention relates to a printed-circuit substrate, such as aTCP (Tape Carrier Package), which is consisted of comb-type electrodesthat are connected to respective comb-type electrodes formed on aliquid-crystal panel, and an integrated circuit for driving theliquid-crystal panel (hereinafter, referred to as IC), and also relatesto its connecting method.

BACKGROUND OF THE INVENTION

Recently, with regard to connecting structure between a liquid-crystalpanel and an external device, printed-circuit substrates, such as TAB(Tape Automated Bonding), FPC (Flexible Printed Circuit) and TCP, havebeen generally employed. IC chips for driving the liquid-crystal panelare assembled on the printed-circuit substrates, thereby achievingcompactness and high functionality. Thus, the packaging density of ICchips is improved in a liquid crystal display wherein these substratesare employed.

Today, in liquid crystal displays having the above-mentionedliquid-crystal panels, thin-width TCPs, which have a smaller gap betweenthe input terminal and the output terminal, have been widely used inorder to further achieve compactness.

For example, as shown in FIGS. 4 and 5, a thin-width TCP, which isformed into a belt shape, is provided with an IC chip 31 that is usedfor driving the liquid-crystal panel. In the thin-width TCP 30, aplurality of output electrodes 32 and input electrodes 33, which arerespectively connected to the terminals of the IC chip 31, are mountedon both sides of the IC chip 31 along the length of the thin-width TCP30.

The output electrodes 32 are formed into a comb shape in an extendingmanner to the left from the IC chip 31 as shown in the drawings. Theinput electrodes 33 are also formed into a comb shape in an extendingmanner to the right from the IC chip 31 as shown in the drawings. Thoseoutput electrodes 32 and the input electrodes 33 are covered with a filmportion 34 and supported thereby.

In the central portion of the thin-width TCP 30 is provided an opening34b through which the IC chip 31 is connected to the output electrodes32 and the input electrodes 33. Ends of the output electrodes 32 and theinput electrodes 33 respectively stick out inside the opening 34b.

The opening 34b is filled with protective resin through a moldingprocess; this allows the IC chip 31 to be connected to the outputelectrodes 32 and the input electrodes 33, and securely fixed therein.Thus, a resin mold section 36 is formed around the IC chip 31.

Further, in the film portion 34 is formed a slit 34a by removing a partof the film portion 34 at the vicinity of the end portion on the inputside. Exposed terminals 33a of the input electrodes 33 are locatedinside the slit 34a so as to be soldered to electrodes of aprinted-circuit substrate or other substrates.

The following description will discuss a connecting method where thethin-width TCP 30 is employed. In the case where the thin-width TCP 30is used for connecting the liquid crystal panel and the printed-circuitsubstrate, the output electrodes 32 and electrodes, not shown, of aliquid crystal panel 40 are first connected respectively as shown inFIG. 6 by the use of an anisotropic conductive film or other materials.

The input electrodes 33, on the other hand, are connected to therespective electrodes 42 through solder 43. Thus, the printed-circuitsubstrate 41 and the liquid crystal panel 40 are electrically connectedto each other through the thin-width TCP 30.

The connection between the thin-width TCP 30 and the printed-circuitsubstrate 41 through the solder 43 is made by using a soldering iron 44.In this case, however, the resin mold section 36, which is formedthrough the molding process of the IC chip 31, protrudes from the backside of the thin-width TCP 30; this protruding resin mold section 36results in a step W_(O) even when the terminals are pressed down by thesoldering iron 44.

This causes the terminals 33a to be lifted from the printed-circuitsubstrate 41, and since the terminals 33a do not contact the electrodes42 well, it is difficult to solder both of them.

Therefore, in a conventional method, the terminals 33a and theelectrodes 42 are soldered while avoiding the influence of the stepW_(O) caused by the protruding resin mold section 36, as shown in FIG.6.

More specifically, the printed-circuit substrate 41 is fixed in aslanted state by using a device for supporting the printed-circuitsubstrate 41, not shown. This arrangement makes it possible to bring theterminals 33a in contact with the electrodes 42 while avoiding theinfluence of the step W_(O) caused by the protruding resin mold section36.

Next, after fixing the resin mold section 36 and the printed-circuitsubstrate 41 by the use of a temporary securing tape 45, the terminals33a and the electrodes 42 are soldered by pressing them to contact oneanother using the tip of the soldering iron 44.

However, this method, which uses the thin-width TCP 30 having theconventional structure and wherein soldering is made by the solderingiron 44 while holding the conventional printed-circuit substrate 41 inthe slanted state, raises the following problems.

(1) Problems associated with the structure of the conventionalthin-width TCP 30:

(a) The film portion 34 in the thin-width TCP 30 has elasticity to acertain degree. Therefore, in the conventional structure wherein theterminals 33a are situated in the slit 34a, the elasticity of the filmportions 34 lying on both sides of the slit 34a in the thin-width TCP 30in the length-wise direction gives adverse effects on the pliability ofthe terminals 33a.

Therefore, even if the terminals 33a are pressed so as to bring theminto contact with the electrodes 42, the terminals 33a tend to be liftedup, resulting in difficulty in contacting both of them.

The contact between them becomes even worse when the printed-circuitsubstrate 41 or the liquid crystal panel 40 has warping or when thethin-width TCP 30 has a curl-distortion in its own structure. Thisresults in reliability problem in the connected structure between them.

(b) In particular, in the printed-circuit substrates such as thin-widthTCPs 30 wherein the IC chip 31 and the slit 34a are closely located,when the thin-width TCP 30 is bent by pressing its terminals 33a usingthe tip of the soldering iron 44, the distortion stress may affect theresin mold section 36 and cause cracking in the resin mold section 36,if the portion of the slit 34a does not have sufficient pliability.

(2) Problems associated with the connecting method:

(a) In the conventional connecting method, since the tip of thesoldering iron 44 has to be brought into contact with the slantingportion, it is difficult to keep the tip stably contacting with theconnecting portion. For this reason, it is hard to obtain stable solderquality and to improve the reliability of the connecting structure.

(b) The soldering iron 44 is susceptible to wear in its tip; this alsomakes it difficult to obtain stable solder quality and to improve thereliability of the connecting structure.

(c) The tip of the soldering iron 44 might be caught by the exposedterminals 33a, causing cutoffs in them especially when the exposedterminals 33a have narrow terminal pitches and are made of thin copperfoil.

(d) As is described in (b) of (1), in the printed-circuit substratessuch as thin-width TCP 30s wherein the IC chip 31 and the slit 34a areclosely located, when the thin-width TCP 30 is bent by pressing itsterminals 33a using the tip of the soldering iron 44, the distortionstress may affect the resin mold section 36 and cause cracking in theresin mold section 36.

SUMMARY OF THE INVENTION

The present invention is devised to solve the above-mentioned problems,and its objective is to provide a printed-circuit substrate whichachieves high reliability in the connecting structure by improving thepliability of the exposed terminals for use in soldering.

Another objective of the present invention is to provide a connectingmethod for printed-circuit substrates by which the reliability ofconnecting structure is improved between the printed-circuit substrate,wherein the pliability of the exposed terminals for use in soldering isimproved, and another printed-circuit substrate.

In order to achieve the above objectives, the printed-circuit substrateof the present invention is provided with: a film-shaped support basehaving an electrical insulating property and elasticity, which includesa resin mold section for supporting an integrated circuit; a pluralityof foil-shaped electric conductors which are connected to the integratedcircuit at their base side and which are supported by the support baseso as to extend toward the periphery of the support base at their tipside; and exposed portions which are provided by removing the supportbase in the direction orthogonal to the foil-shaped electric conductorsover an entire area of the support base between the integrated circuitand the periphery of the support base so as to expose one portion ofeach foil-shaped electric conductor.

In the above arrangement, the support base is divided into two portions,that is, one side having the integrated circuit and the other sidecorresponding to the periphery side, with the exposed portions locatedin between.

In the case of connecting the foil-shaped electric conductors to, forexample, electrodes of a printed-circuit substrate, it is necessary tobring the foil-shaped electric conductors in contact with the respectiveelectrodes through solder.

Here, the resin mold section protrudes from the undersurface of thefilm-shaped support base. Because of this protruding resin mold section,when the foil-shaped electric conductors on the periphery side in thesupport base are connected to an external device, it is difficult tokeep them on the same plane as the foil-shaped electric conductors onthe integrated circuit side in the support base. Therefore, it isnecessary to hold the foil-shaped electric conductors on the integratedcircuit side in the support base and the foil-shaped electric conductorson the periphery side in the support base at different planes.

In order to avoid the influence of the protruding resin mold section, aneffective method is to bend the exposed portions so that the foil-shapedelectric conductors are smoothly aligned with the respective electrodes.

In the conventional arrangement, however, in order to bend the exposedterminals, or the foil-shaped electric conductors, it was necessary toalso bend the film portion, or the support base for supporting theexposed terminals. This arrangement made it difficult to keep theexposed terminals in contact with the respective electrodes due to therestoring force of the bent film portion.

Further, in the conventional arrangement, if a greater force strongenough to oppose the restoring force was applied so as to make both ofthem in contact, the restoring force would come to affect the resin moldsection through the film portion; this tended to cause cracking in theresin mold section.

However, in the above-mentioned arrangement, since the portion of thesupport base is removed in the direction orthogonal to the foil-shapedelectric conductors over the entire area thereof, the support basehaving elasticity does not exist in the adjacent areas in the directionorthogonal to the foil-shaped electric conductors.

Therefore, in the case of bringing the foil-shaped electric conductorsinto contact with the electrodes and soldering both of them, it ispossible to prevent the foil-shaped electric conductors from beinglifted up and separated from the electrodes due to the restoring forceof the support base, which is different from the conventionalarrangement.

As described above, by improving the pliability of the exposed portions,the above-mentioned arrangement achieves high adhesion between thefoil-shaped electric conductors and the electrodes. As a result, whenelectrical connection is made between the foil-shaped electricconductors and the electrodes by means of soldering, the reliability ofthe connecting structure is improved.

Moreover, different from the conventional arrangement, theabove-mentioned arrangement makes it possible to prevent the stress thatis imposed on the resin mold section due to the restoring force from thebent film portion; this reduces cracking that might occur in the resinmold section. Thus, when applied to connections between printed-circuitsubstrates such as used in liquid crystal displays, etc., theabove-mentioned arrangement reduces the possibility of defectiveproducts in manufacturing liquid crystal displays or other apparatuses.

In order to achieve another objective of the present invention, theconnecting method for printed-circuit substrates of the presentinvention, which uses a printed-circuit substrate having first andsecond support bases, a resin mold section for fixing an integratedcircuit supported by the first support base, and a plurality offoil-shaped electric conductors that are installed on the first andsecond support bases and connected to the integrated circuitrespectively so as to connect the first and second support bases in aseparated manner with each other, is provided with the step of solderingthe foil-shaped electric conductors on the second support base bypressing and heating the second support base.

In this method, by bending the foil-shaped electric conductors exposedbetween the first and second support bases, the second support base isshifted with respect to the first support base during the pressing andheating process so that both of the bases are situated at the differentplanes.

In this case, neither the first support base nor the second support baseis located along an area corresponding to a line connecting the bentpoints of the foil-shaped electric conductors and its extended line.Therefore, even if the foil-shaped electric conductors are bent, thefirst and second support bases are not bent.

Moreover, in the case where the foil-shaped electric conductors of thefirst and second support bases are respectively connected to externaldevices, the resin mold section, which protrudes from the surface of thefirst support base, makes it difficult for the foil-shaped electricconductors of the first and second support bases to be aligned on thesame plane so as to be connected. Therefore, it is necessary to hold thefoil-shaped electric conductors of the first and second support bases atdifferent planes.

Here, in the case where the foil-shaped electric conductors of thesecond support base are connected, for example, to electrodes on aprinted-circuit substrate by means of soldering, the above-mentionedmethod prevents the restoring force that is caused by the bent filmportion, which is a conventional form of the support base. Thiseliminates the necessity of having to take into consideration therestoring force that is exerted on the foil-shaped electric conductorsand the electrodes in their separating directions.

With this method, when the foil-shaped electric conductors of the secondsupport base are soldered, for example, to electrodes of aprinted-circuit substrate by applying pressure and heat, the solderingprocess is carried out with both of them securely made contact with eachother, thereby improving the reliability of the connection between them.

Furthermore, in the above-mentioned method, it is not necessary to heatup the exposed foil-shaped electric conductors for soldering; thiseliminates the necessity of having to take into consideration the lengthof the foil-shaped electric conductors with regard to the soldering.Therefore, it is not necessary to provide long length for the exposedportions of the foil-shaped electric conductors, thereby making itpossible to miniaturize the entire structure consisting of the first andsecond support bases.

Therefore, the pliability of the exposed portions of the foil-shapedelectric conductors is improved so that two bent positions are providedin each of those portions. Thus, the second support base, which becomesmovable by pressure and heat, is maintained horizontally without thenecessity of having to maintain it in a slanted state to the firstsupport base as is conventionally done. This makes it possible tostabilize the state of the second support base when it is pressed duringthe pressing and heating process, thereby allowing a stable solderingprocess.

Further, since the exposed portions are not pressed and heated, it ispossible to prevent cutoffs caused when the tip of the soldering iron iscaught on the exposed portion during the pressing and heating process.As described above, the above-mentioned method further improves thereliability of the connection between the foil-shaped electricconductors of the second support base and, for example, electrodes of aprinted-circuit substrate.

In addition to the above method, a pressing and heating means forpressing and heating the second support base may be provided, and a filmmaterial for preventing contaminants from adhering to the pressing andheating means may be sandwiched between the pressing and heating meansand the second support base.

In this method, it is possible to prevent contaminants such as solderfragments or flux from adhering to the tip of the pressing and heatingmeans. Therefore, it is not necessary to clean the tip by using agrindstone, sandpaper or a brush, thereby preventing the tip fromwearing out. As a result, the shape of the pressing and heating means iswell maintained, and stable pressing and heating conditions areobtained. The use of this connecting method further improves thereliability of the connection, as well as extending the life of thepressing and heating means.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a thin-width TCP that is used as aprinted-circuit substrate of the present invention.

FIG. 2 is a cross-sectional view of the thin-width TCP.

FIG. 3, which is an explanatory drawing that shows the thin-width TCP ofFIG. 2 for connecting a liquid crystal panel and a printed-circuitsubstrate, also illustrates a state in which the input electrodes of thethin-width TCP and the electrodes of the printed-circuit substrate aresoldered and a connecting device used in the soldering process.

FIG. 4 is a plan view of a conventional thin-width TCP.

FIG. 5 is a cross-sectional view of the thin-width TCP.

FIG. 6 is an explanatory drawing that shows a state wherein the inputelectrodes of the thin-width TCP of FIG. 5, to which a liquid crystalpanel is connected, and electrodes of a printed-circuit substrate aresoldered.

DESCRIPTION OF THE EMBODIMENTS

Referring to FIGS. 1 through 3, the following description will discussone embodiment of the present invention.

As illustrated in FIGS. 1 and 2, a printed-circuit substrate of thepresent embodiment is provided with a thin-width TCP 10 which is formedinto a thin rectangular shape. Hereinafter, longer sides of thethin-width TCP 10 are referred to as sides and shorter sides thereof arereferred to as ends. The thin-width TCP 10 is used for connecting, forexample, a liquid crystal panel and a printed-circuit substrate forreleasing signals to drive the panel, and is provided with an IC chip 11for driving the liquid crystal panel.

The IC chip 11, which has a virtually rectangular parallelopiped shape,is fixed in the center of the thin-width TCP 10 so that the length-wisedirection of the IC chip 11 coincides with the length-wise direction ofthe thin-width TCP 10.

The TCP 10 is provided with a plurality of input electrodes 12 and aplurality of output electrodes 13 that are respectively connected to theterminals of the IC chip 11. Those input electrodes 12 and outputelectrodes 13 are made of foil-shaped electric conductors, and areformed into a belt-like shape. The materials of the foil-shape electricconductors are gold, silver, aluminum, copper, and their alloys, as wellas light-transmitting electric conductors such as indium tin oxide.

The output electrodes 12 are respectively disposed from the terminals ofthe IC chip 11 to one side of the thin-width TCP 10, that is, in anextending manner to the left in the drawing.

The input electrodes 13, on the other hand, are respectively disposedfrom the terminals of the IC chip 11 to the other side of the thin-widthTCP 10, that is, in an extending manner to the right in the drawing.

Those output and input electrodes 12 and 13 are covered with a filmportion 14 made of a resin film from above, and supported by the filmportion 14. In this manner, the output and input electrodes 12 and 13are formed under the film portion 14, and located along the film portion14 in the length-wise direction.

The output and input electrodes 12 and 13 are aligned virtually inparallel with one another in the proximity of the sides of the filmportion 14, and arranged in the length-wise direction of the filmportion 14 with virtually the same interval between them. In otherwords, the output and input electrodes 12 and 13 are respectivelyarranged into a comb shape in the proximity of the sides of the filmportion 14.

The film portion 14 has flexibility which allows it to be freely bent,elasticity, and heat resistance. The resistance to heat of the filmportion 14 is provided in such a degree that its property is not alteredeven after having been subjected to heat applied by solder 3 so as toconnect the input electrodes 13 for a predetermined period of time, forexample, for two or three minutes (see FIG. 3)

An opening 14b for holding the IC chip 11 therein is formed in thecenter of the film portion 14. The end portions of the output and inputelectrodes 12 and 13 stick out and are exposed inside the opening 14b.

The opening 14b is filled with protective resin such as epoxy resinthrough a molding process; this allows the IC chip 11 to be securelyfixed and connected to the base portions of the output and inputelectrodes 12 and 13. Thus, a resin mold section 16 is formed around theIC chip 11.

Further, in the film portion 14, is provided a removed section 14a thatruns from end to end in the direction orthogonal to the input electrodes13, that is, over an entire area along the length of the film portion14.

In the removed section 14a, are located exposed terminals 13a which arethe exposed forms of the input electrodes 13. The exposed terminals 13aare used when the input electrodes 13 are soldered to electrodes 7 of aprinted-circuit substrate 6, which will be described later (see FIG. 3).

In this manner, the film portion 14 is constituted of a main filmportion 14c having the IC chip 11 and a belt-like peripheral filmportion 14d that is separated from the main film portion 14c andconnected thereto through the exposed terminals 13a.

The peripheral film portion 14d is disposed virtually in parallel withthe main film portion 14c in the length-wise direction of the filmportion 14. The peripheral film portion 14d thus maintains the exposedterminals 13a with the same interval between them by holding the tips ofthe input electrodes 13, thereby preventing contact between the exposedterminals 13a.

Moreover, inside the removed section 14a, are provided a pair ofsupporting terminals 13b for reducing a mechanical load that is to beimposed on the exposed terminals 13a connecting the main film portion14c and the peripheral film portion 14d.

The supporting terminals 13b, each of which is a foil-shaped electricconductor made of a material such as copper foil and has a width widerthan that of the exposed terminals 13a, are respectively installed onboth ends of the exposed terminals 13a in parallel with them.

The supporting terminals 13b support the peripheral film portion 14d;this makes it possible to reduce the mechanical load imposed on theexposed terminals 13a that support the peripheral film portion 14d,thereby preventing cutoffs in the exposed terminals 13a due to themechanical load.

Next, the following description will discuss a connecting method whereina liquid crystal panel 5, provided as a liquid crystal display device,and a printed-circuit substrate 6 for driving the liquid crystal panel 5are connected to each other by using the above-mentioned thin-width TCP10.

As shown in FIG. 3, the printed-circuit substrate 6 is provided with aplurality of electrodes 7 in positions corresponding to those inputelectrodes 13 installed in the thin-width TCP 10. The liquid crystalpanel 5, on the other hand, is provided with a plurality ofliquid-crystal-panel electrodes, not shown, in positions correspondingto those output electrodes 12 installed in the thin-width TCP 10.

Here, in the case of connecting the thin-width TCP 10, theprinted-circuit substrate 6, and the liquid crystal panel 5 to oneanother so as to construct, for example, a liquid crystal display, sincethe resin mold section 16 has a protruding form, it is necessary toshift the peripheral film portion 14d with respect to the main filmportion 14c to be located on a different plane.

First, the liquid-crystal-panel electrodes of the liquid crystal panel 5and the output electrodes 12 of the thin-width TCP 10 are electricallyconnected respectively through an anisotropic conductive film.

These connections are made as follows: an anisotropic conductive filmhaving a predetermined thickness, not shown, is formed on theliquid-crystal-panel electrodes of the liquid crystal panel 5; theoutput-side of the thin-width TCP 10 are positioned and superimposedonto the anisotropic conductive film so that the output electrodes 12are aligned face to face with the corresponding liquid-crystal-panelelectrodes; and contact bonding with heat is made by pressing a heatingtool or the like from the thin-width TCP 10 side.

Next, the input electrodes 13 in the thin-width TCP 10 are electricallyconnected to the respective electrodes 7 of the printed-circuitsubstrate 6 through solder 3 by using a connecting device such as apulse heat bonder.

Here, an explanation will be given on the connecting device that is usedfor soldering the input electrodes 13 and the electrodes 7. Asillustrated in the drawing, the connecting device is provided with asubstrate supporting plate 4 whereon the printed-circuit substrate 6 isplaced, a heating tool 1 located above the substrate supporting plate 4which is provided as the pressing and heating means, and a cleaning film(film material) 2 that is placed between the tip face of the heatingtool 1 and the substrate supporting plate 4.

The heating tool 1, which is driven to move up and down on demand, is ofa pulse heating type wherein a pulse current is flown instantaneouslyonly upon pressing process so as to apply heat instantaneously.

The cleaning film 2 is made of an extremely thin organic film such as apolyamide resin film, especially aromatic polyamide resin film, and hasthe property of heat resistance with a low coefficient of linearexpansion. The cleaning film 2, which has a long tape shape, is sentfrom one side to the other by a predetermined length every time it isused, and is then reeled up. In this manner, the cleaning film 2 is usedwhile contacting a heating face provided on the tip of the heating tool1.

When soldering is made to connect the input electrodes 13 and theelectrodes 7 by using the above-mentioned connecting device, theprinted-circuit substrate 6 is first placed on the substrate supportingplate 4, and solder 3 is put on the electrodes 7 of the printed-circuitsubstrate 6, as well as applying flux thereto in order to improve itsconnecting property.

Here, prior to putting the solder 3 thereon, resist 9 is respectivelyapplied to predetermined areas on the electrodes 7 of theprinted-circuit substrate 6 and the input electrodes 13 of thethin-width TCP 10, that is, to areas from the terminals 13a to the ICchip 11 in order to prevent adhesion of the solder 3.

Then, positioning is made so that the input electrodes 13 of thethin-width TCP 10 and the corresponding electrodes 7 are aligned face toface with one another, and the thin-width TCP 10 and the printed-circuitsubstrate 6 are laminated with the solder 3 sandwiched in between, andthen both of them are temporarily fixed by the use of a temporary fixingtape 8 that is preliminarily affixed onto the printed-circuit substrate6.

Next, the heating tool 1 is pressed on the peripheral film portion 14dwith the cleaning film 2 sandwiched in between so that the solder 3 isheated up instantaneously and melted down, and then the solder 3 coolsoff.

In this manner, the electrodes 7 and the input electrodes 13 areelectrically connected. After the solder 3 has cooled off below itsmelting point, the heating tool 1 is raised, and the cleaning film 2 isreeled up by the predetermined length in the predetermined direction.Thus, the cleaning film 2 to contact the tip face of the heating tool 1is updated.

As described above, in the thin-width TCP 10 of the present embodiment,the removed section 14a, which is formed for exposing the exposedterminals 13a, is provided in such a manner that it runs from end to endin the direction orthogonal to the input electrodes 13, that is, over anentire belt-like area along the length of the film portion 14.Therefore, no film portion 14 exists on either area adjacent to the setof the exposed terminals 13a in the length-wise direction of thethin-width TCP 10.

Therefore, even if the exposed terminals 13a made of copper foil orother materials are bent, it is possible to prevent the restoring forcethat is caused by the elasticity of the film portion 14, which isdifferent from the conventional arrangement. This allows the exposedterminals 13a to be plastically deformed with ease. As a result, thepliability of the thin-width TCP 10 is improved in its area where theexposed terminals 13a are located, in comparison with the conventionalarrangement.

With this arrangement, when soldering is made between the tips of theinput electrodes 13 of the thin-width TCP 10 and the electrodes 7, theinput electrodes 13 located on the undersurface of the peripheral filmportion 14d and the electrodes 7 on the printed-circuit substrate 6 areeasily brought into contact with each other with the solder 3 sandwichedin between by bending the exposed terminals 13a.

In the thin-width TCP 10, the IC chip 11 is supported inside the opening14b by the resin mold section 16. Further, in order that the thin-widthTCP 10 holds the resin mold section 16 firmly, the resin mold section 16is formed in such a manner as to sandwich the surrounding portion of theopening 14b from above and from under. This arrangement causes the resinmold section 16 to protrude from the surface and undersurface of thethin-width TCP 10.

In the case of connecting the input electrodes 13 of the thin-width TCP10 to the electrodes 7 by means of soldering, the printed-circuitsubstrate 6 is brought close to the liquid crystal panel 5 to bepositioned under the resin mold section 16 so as to achieve compactness;therefore, the printed-circuit substrate 6 is located face to face withthe resin mold section 16.

However, in conventional methods, when the exposed terminals of a TCPhaving such a resin mold section are connected to the electrodes of aprinted-circuit substrate, the exposed terminals of the TCP are bent sothat the exposed terminals are brought in close contact with theelectrodes in order to achieve compactness as described above as well asavoiding the influence of the protruding structure of the resin moldsection.

When the exposed terminals are bent, it is also necessary to bend thefilm portion that supports the exposed terminals. For this reason, it isdifficult to make the exposed terminals and the electrodes in contactwith each other due to the restoring force of the bent film portion.

Moreover, if a greater force is applied against the restoring force inorder-to make them in contact, the restoring force imposed on the resinmold section increases; this might cause cracking in the resin moldsection.

However, in the arrangement of the present embodiment, no film portions14a exist on either side of the set of the exposed terminals 13a in thedirection orthogonal to the exposed terminals 13a. For this reason, evenif the exposed terminals 13a are bent, there is no film portion 14a tobe bent.

Therefore, in the case of bringing the tips of the input electrodes 13into contact with the electrodes 7 and soldering both of them, it ispossible to prevent the input electrodes 13 from being lifted up andseparated from the electrodes 7 due to the restoring force of the filmportion provided as the support base, which is different from theconventional arrangement.

Further, the pliability of the exposed terminals 13a is improved so thattwo bent positions are provided in them; this makes it possible tomaintain the peripheral film portion 14d horizontally even when it isshifted with respect to the main film portion 14c. This arrangementeliminates the necessity of having to maintain the printed-circuitsubstrate in a slanted state as is conventionally done. This arrangementalso makes it possible to stabilize the state of the peripheral filmportion 14d when it is pressed and heated, thereby improving the contactbetween the input electrodes 13 and the electrodes 7.

Thus, soldering is securely made between the input electrodes 13 and theelectrodes 7 by applying heat and pressure to the peripheral filmportion 14d that supports the input electrodes 13 by the use of theheating tool 1.

Consequently, the arrangement and method of the present embodiment,wherein the liquid crystal panel 5 and the printed-circuit substrate 6are brought in close contact with each other so as to be electricallyconnected, make it possible to achieve compactness, as well as improvingthe reliability of the connection between the input electrodes 13 andthe electrodes 7.

At the same time, since the exposed terminals 13a has high pliabilityand since no restoring force is applied by the elasticity of the filmportion 14, different from the conventional arrangements, neitherdistortion stress nor restoring force is transmitted to the main filmportion 14c when the exposed terminals 13a are bent. Therefore, therestoring force or other forces is not imposed on the resin mold section16 that supports the IC chip 11 on the main film portion 14c, therebyeliminating cracking that might occur in the resin mold section 16.

Moreover, in the present embodiment, soldering is made between the inputelectrodes 13 of the thin-width TCP 10 and the electrodes 7 of theprinted-circuit substrate 6 by applying heat and pressure to theperipheral film portion 14d by the use of the heating tool 1; therefore,this arrangement eliminates the necessity of having to heat the exposedterminals 13a by pressing the heating tool 1 directly onto the exposedterminals 13a inside the removed section 14a. This makes it possible toprevent cutoffs that tend to occur when the exposed terminals 13a arepressed.

As described above, the arrangement and method of the present embodimentimprove the reliability of the connecting structure in the liquidcrystal display wherein, for example, the thin-width TCP 10 is employed,thereby contributing to high yield of the liquid crystal display.

Furthermore, as to the heating tool 1, a no-cut tool with a wide width,which is easily produced by a machining process at low cost and hasstable heating characteristics, may be employed.

Different from the conventional method wherein the heating tool 1 isbrought inside the removed section 14a during the connecting operation,it is not necessary for the above-mentioned method to machine theheating tool 1 so as to impart a thin width; therefore, an effectiveconnecting operation is available without being influenced by the shapeand the machining limitations of the tool.

At the same time, the method of the present embodiment eliminates thenecessity of having to bring the heating tool 1 into the removed section14a with high positioning precision, thereby simplifying theconstruction of the connecting device.

In the conventional methods, the heating tool 1 has to be prepared bycut-out machining it so as to be exclusively adapted to each kind andthe number of the thin-width TCPs 10 as well as to the array pitch ofeach thin-width TCP 10, and when the heating tool 1 is exchanged, it isnecessary to take into consideration the balance of the heating tool 1.However, the method of the present embodiment eliminates thesenecessities, thereby cutting cost required for the connecting process aswell as improving the efficiency of work.

Further, in the connecting device of the present invention, the cleaningfilm 2 for covering the tip of the heating tool 1 is provided; thisarrangement prevents contaminants such as fragments of solder 3 or fluxfrom adhering to the tip of the heating tool 1.

Therefore, it is not necessary to clean the tip of the heating tool 1 byusing a grindstone, sandpaper or a brush, thereby preventing the tipfrom wearing out during the cleaning process. As a result, the shape ofthe tip of the heating tool 1 is well maintained, thereby providingstable pressing and heating conditions. The use of the heating tool 1for the connecting process further improves the reliability of theconnection, as well as extending the life of the heating tool 1.

The above-mentioned arrangement prevents the adhesion of solder onto thetip of the heating tool 1; therefore, in the case of forming the heatingtool 1 into a long-length one-bar shape, it is not necessary to employtitanium as the material of the heating tool 1. Instead of titaniumwhich has an anti-adhering property to solder although its temperaturedistribution is unstable, superinvar having stable heatingcharacteristics may be adopted.

As a result, it becomes possible to solder many of those thin-width TCPs10 in a batch process by the use of the heating tool 1 having thelong-length one-bar shape, thereby improving the productivity to a greatdegree.

Moreover, since it is not necessary to shape the heating tool 1 to havea multi-blade structure such as a short, divided titanium tool, noexchange in types of the tool is required for any kinds and the numberof the thin-width TCPs 10 as well as for any array pitch of thethin-width TCP 10.

Here, in the case of the heating tools having the multi-blade structuresuch as a divided titanium tool, since it is very difficult to keepbalances of pressure among the heating tools, exchange is required foreach shank of the tool mounting base; this raises many problems such aslow efficiency of work, high cost, and expensive managing cost.

Additionally, in the present embodiment, the method is adopted, whereinsoldering is made by pressing and heating the peripheral film portion14d by the use of the heating tool 1; yet, the conventional method,wherein soldering is made by using a soldering iron while holding theprinted-circuit substrate 6 in a slanted state, may be adopted.

Even in the case of adopting the conventional connecting method, thearrangement of the present embodiment prevents the exposed terminals 13afrom being lifted up from the electrodes 7, thereby improving thecontact between them, as well as reducing cracking that might occur inthe resin mold section 16.

Moreover, in the present embodiment, the heating tool 1 of apulse-heating type is employed as the heating means; therefore,instantaneous heating and cooling processes are available. In comparisonwith a heating method using heat-resistant glass through whichlight-related heating such as provided by infrared rays is applied,since the temperature of the heating tool is directly detected andcontrolled, this arrangement makes it possible to provide easier jobcontrol, obtain soldering of high quality, improve the reliability ofthe connection by soldering, and improve the efficiency of work.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A connecting method for a printed-circuitsubstrate, wherein the printed-circuit substrate includes film-shapedfirst and second support bases having an electrical insulating propertyand elasticity; a resin mold section for securely fixing an integratedcircuit supported on the first support base; and a plurality offoil-shaped electric conductors that are connected to the integratedcircuit and installed on the first and the second support bases suchthat the first and the second support bases are connected to each otherby the foil-shaped electric conductors, comprising the step of:solderingthe foil-shaped electric conductors by applying heat and pressure to thesecond support base.
 2. The connecting method for the printed-circuitsubstrate as defined in claim 1, wherein the first support base has anopening wherein the base ends of the foil-shaped electric conductors areexposed and the integrated circuit is supported by the resin moldsection.
 3. The connecting method for the printed-circuit substrate asdefined in claim 1, wherein the first and the second support bases areformed into thin-width rectangular shapes, the second support base beingdisposed with respect to the first support base such that the longerside of the second support base are virtually parallel to the longerside of the first support base.
 4. The connecting method for theprinted-circuit substrate as defined in claim 3, wherein the foil-shapedelectric conductors connecting the first and the second support basesare arranged virtually in parallel with one another.
 5. The connectingmethod for the printed-circuit substrate as defined in claim 3, whereinthe foil-shaped electric conductors include those of a type which extendfrom the base ends, cross one of the longer sides of the second supportbase facing the first support base, and reach a peripheral edgecorresponding to the other longer side.
 6. The connecting method for theprinted-circuit substrate as defined in claim 5, wherein the foil-shapedelectric conductors are parallel to one another at the peripheral edge.7. The connecting method for the printed-circuit substrate as defined inclaim 1, further comprising the preliminary step of:prior to said step,placing the second support base so that it is pressed and heated from asurface opposite to the surface whereon the foil-shaped electricconductors are supported.
 8. The connecting method for theprinted-circuit substrate as defined in claim 1, further comprising thesteps of:providing a pressing and heating means for pressing and heatingthe second support base; and placing a film member for preventingcontaminants from adhering to the pressing and heating means between thepressing and heating means and the second support base, upon pressingand heating the second support base by the use of the pressing andheating means.
 9. The connecting method for the printed-circuitsubstrate as defined in claim 8, further comprising the post-stepof:updating the film member after said process.